The present invention generally relates to a mechanism for tool for removing and installing a threshing concave from and to a threshing machine, such as a combine harvester. In particular it relates to a dedicated tool and a method for removing and installing a concave underneath the threshing drum inside the machine housing.
Modern combine harvesters can be used for harvesting and threshing a wide range of agricultural products. However, for optimal performance, it is necessary to install components that are more appropriate for the one or other crop type. For example, wheat, barley and rye can be threshed using a drum provided with axially extending rasp bars and a small grain concave having slats extending parallel to the drum axis. For threshing maize (corn), the same drum may be used but the concave should be replaced with a concave having larger apertures between the slats and the wires. Rice requires a drum provided with radially extending teeth and a concave with corresponding, inwardly extending teeth. Accordingly, the transition from one crop type to another often entails the removal of one concave and the installation of a different concave.
The drum and the concave are subject to wear and have to be repaired or replaced at regular intervals to maintain threshing efficiency. This exchange action also requires removal and installation of the concaves.
In recent years, the handling of the concaves has become more cumbersome because of the larger dimensions and hence the increased weight of the concave. Meanwhile, operators have become more demanding and are looking for more comfort and convenience.
This problem may be solved by splitting the concave into three or four more manageable concave sections that are slid into a concave frame that remains attached to the frame. Such structure requires a sturdy concave frame. It also multiplies the total number of attachment points for the concave sections.
Mechanism may be provided for supporting the concave during its movement inside the threshing housing. U.S. Pat. No. 3,871,384 shows the threshing apparatus of an axial flow combine harvester. Supports at the front and rear ends of the concave enable the transport of the concave to an aperture in a side wall of the harvester. However no mechanism are provided for facilitating the removal of the concave from the housing.
In the axial flow combine harvester shown in U.S. Pat. No. 3,470,881 the concave is mounted to a pair of sliding arms that remain attached to the combine. The concave frame cannot be removed from the combine but it can be moved to a service position outside the housing for repairing or replacing the concave bars and wires. For heavier concaves additional support is provided by a movable carriage assembly that adds to the complexity of the machine.
It is an object of the present invention to provide a tool and a method that facilitate the manual transfer of a heavy concave from an operative position underneath the threshing drum to a position outside the threshing housing.
In accordance with the first embodiment of this invention, there is provided a mechanism for the removal of a threshing concave from a threshing machine comprising a housing and a rotatable threshing drum mounted inside said housing. The mechanism comprises a pair of spaced support arms for slideably receiving thereon end sections of a threshing concave,
characterised in that at least one of the support arms is provided with mechanism for attachment of arm to the housing. The inner arm section extends to one side of the attachment mechanism for supporting the concave inside the housing when the support arm is attached to the housing. An outer arm section extends to the other side of the attachment mechanism for supporting a threshing concave outside the housing when the support arm is attached to the housing.
This mechanism enables the movement of the concave between an operative position below the threshing drum and an accessible position outside the threshing housing.
Preferably, the attachment mechanism comprise pivot mechanism, such as a bushing, allowing pivoting of the inner arm section between an upper position close to the threshing drum and a lower position, more remote from the threshing drum. This helps to reduce the distance between the concave and the support arms when the concave is disconnected from the adjustment mechanism for the concave clearance.
The support arm may be provided with positioning mechanism for placing the inner arm section in the upper or lower position. Such positioning mechanism may comprise a disc that is linked by an eccentric, pivotable connection to the inner arm section. The disc may have an outer diameter adapted to fit in an oblong aperture of the housing wall. The arm may be lifted or lowered by rotating the disc over 180 degrees.
Preferably, the positioning mechanism also comprises a securing mechanism for holding the inner arm section in the upper or lower position. This prevents unwanted tilting of the arms whilst the concave is moved inwardly or outwardly. The positioning mechanism can comprise a pin extending through the disc and urged towards the arm by a resilient mechanism. For example, a spring, for engaging a matching hole in the inner arm section.
In order to keep the disc aligned with the housing wall, the disc may be provided with alignment structure. For example, a circular border having an outer diameter exceeding the smaller of the width or the height of the aperture in the wall.
To ensure that the concave does not slip off the outer arm sections, these may have retaining mechanism, such as guide plates attached to one side or both sides of the arm and an upward ear at the front end of the arm.
According to another aspect of the present invention, there is provided a method for removal and installation of a threshing concave from and to a threshing machine comprising a housing, a rotatable threshing drum mounted inside the housing and a clearance adjustment mechanism for the concave, the method comprising the steps of attaching to the housing mechanism comprising at least one support arm such that an inner arm section extends below the concave and an outer arm section extends outwardly from the housing. Lowering the concave to a position on or adjacent to the inner arm section and releasing the concave from the adjustment mechanism to let the concave rest on the inner arm section. Sliding the concave along the inner and outer arm sections to a position outside the housing. Removing the concave from the outer arm section; and removing the mechanism from the housing.
Preferably, the concave lowering step is preceded by the steps of raising the inner arm section to a position close to the concave and securing the arm in this position. This limits the movement of the concave when it is released from its adjustment mechanism.
Before the concave is slid outwardly, it is advantageous to lower the inner arm section to a position more remote from the threshing drum.
For installation of a concave the following method can be used of attaching a support arm to the housing such that the inner arm section extends below the concave and the outer arm section extends outwardly from the housing. Placing a threshing concave on the outer arm section. Sliding the concave along the outer and inner arm sections into the housing to a position below a threshing drum. Connecting the concave to the adjustment mechanism and raising the concave to lift it off the inner arm section; and removing the mechanism from the housing.
Before the concave is slid inwardly, it is advantageous to lower the inner arm section and to secure it in this lower position. The concave may be connected to the adjustment mechanism after jointly raising the inner arm section and the concave resting thereon and securing the inner arm section in this upper position.
In case the support arm is provided with an eccentric disc, the support arm may be attached to the housing by aligning the disc with the housing wall. This aligning substep may comprise: inclining the disc; inserting the disc from within the housing through an aperture in the housing wall; hooking a border of the disc behind a rim of the aperture; and raising the disc to a vertical position.
Where the disc is connected to the inner arm section by an eccentric, pivotable connection, the raising or lowering step may comprise rotating the disc to raise or lower the eccentric connection. It is also possible to secure the position of the support arm by securing the disc to the inner arm section.